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/* fmemopen implementation.
Copyright (C) 2015-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
/* fmemopen() from 2.22 and forward works as defined by POSIX. It also
provides an older symbol, version 2.2.5, that behaves different regarding
SEEK_END (libio/oldfmemopen.c). */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include "libioP.h"
typedef struct fmemopen_cookie_struct fmemopen_cookie_t;
struct fmemopen_cookie_struct
{
char *buffer; /* memory buffer. */
int mybuffer; /* allocated my buffer? */
int append; /* buffer open for append? */
size_t size; /* buffer length in bytes. */
off64_t pos; /* current position at the buffer. */
size_t maxpos; /* max position in buffer. */
};
static ssize_t
fmemopen_read (void *cookie, char *b, size_t s)
{
fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
if (c->pos + s > c->maxpos)
{
s = c->maxpos - c->pos;
if ((size_t) c->pos > c->maxpos)
s = 0;
}
memcpy (b, &(c->buffer[c->pos]), s);
c->pos += s;
return s;
}
static ssize_t
fmemopen_write (void *cookie, const char *b, size_t s)
{
fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;;
off64_t pos = c->append ? c->maxpos : c->pos;
int addnullc = (s == 0 || b[s - 1] != '\0');
if (pos + s > c->size)
{
if ((size_t) (c->pos + addnullc) >= c->size)
{
__set_errno (ENOSPC);
return 0;
}
s = c->size - pos;
}
memcpy (&(c->buffer[pos]), b, s);
c->pos = pos + s;
if ((size_t) c->pos > c->maxpos)
{
c->maxpos = c->pos;
if (c->maxpos < c->size && addnullc)
c->buffer[c->maxpos] = '\0';
/* A null byte is written in a stream open for update iff it fits. */
else if (c->append == 0 && addnullc != 0)
c->buffer[c->size-1] = '\0';
}
return s;
}
static int
fmemopen_seek (void *cookie, off64_t *p, int w)
{
off64_t np;
fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
switch (w)
{
case SEEK_SET:
np = *p;
break;
case SEEK_CUR:
np = c->pos + *p;
break;
case SEEK_END:
np = c->maxpos + *p;
break;
default:
return -1;
}
if (np < 0 || (size_t) np > c->size)
{
__set_errno (EINVAL);
return -1;
}
*p = c->pos = np;
return 0;
}
static int
fmemopen_close (void *cookie)
{
fmemopen_cookie_t *c = (fmemopen_cookie_t *) cookie;
if (c->mybuffer)
free (c->buffer);
free (c);
return 0;
}
FILE *
__fmemopen (void *buf, size_t len, const char *mode)
{
cookie_io_functions_t iof;
fmemopen_cookie_t *c;
FILE *result;
c = (fmemopen_cookie_t *) calloc (sizeof (fmemopen_cookie_t), 1);
if (c == NULL)
return NULL;
c->mybuffer = (buf == NULL);
if (c->mybuffer)
{
c->buffer = (char *) malloc (len);
if (c->buffer == NULL)
{
free (c);
return NULL;
}
c->buffer[0] = '\0';
}
else
{
if (__glibc_unlikely ((uintptr_t) len > -(uintptr_t) buf))
{
free (c);
__set_errno (EINVAL);
return NULL;
}
c->buffer = buf;
/* POSIX states that w+ mode should truncate the buffer. */
if (mode[0] == 'w' && mode[1] == '+')
c->buffer[0] = '\0';
if (mode[0] == 'a')
c->maxpos = strnlen (c->buffer, len);
}
/* Mode | starting position (cookie::pos) | size (cookie::size)
------ |----------------------------------|-----------------------------
read | beginning of the buffer | size argument
write | beginning of the buffer | zero
append | first null or size buffer + 1 | first null or size argument
*/
c->size = len;
if (mode[0] == 'r')
c->maxpos = len;
c->append = mode[0] == 'a';
if (c->append)
c->pos = c->maxpos;
else
c->pos = 0;
iof.read = fmemopen_read;
iof.write = fmemopen_write;
iof.seek = fmemopen_seek;
iof.close = fmemopen_close;
result = _IO_fopencookie (c, mode, iof);
if (__glibc_unlikely (result == NULL))
{
if (c->mybuffer)
free (c->buffer);
free (c);
}
return result;
}
libc_hidden_def (__fmemopen)
versioned_symbol (libc, __fmemopen, fmemopen, GLIBC_2_22);
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